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The proposed project is seeking for a better understanding of the in situ stress spatial variations near faults, in the context of improving hydraulic stimulation and mitigating seismicity in reservoirs for geothermal systems (and/or hydrocarbons, waste disposal), as faults act as both fluid conduits and earthquake sources. This project is closely associated with the field experiments of the SCCER-SoE in the planned Bedretto Underground Laboratory, which serves as a key step to address the Swiss Energy Strategy by 2050 for 7% geothermal energy. Primarily, the project strives to tackle the following challenges (among others):1To what extent do the in situ stresses rotate and vary approaching, and within, the fault zone? Are stress variations scale-invariant? (field aspect)2To what extent do lithology and fault structure variations induce stress changes? Is visco-plastic stress relaxation or elasticity contrast the main cause for stress variations, or could it be something else? (laboratory aspect)3Can we predict the spatial (and temporal) stress variations, given the knowledge of the far-field stress state and fault structure? Accordingly, how can the knowledge on stress variations improve the 'steering' of hydraulic fracturing/shearing and mitigate seismicity? (theoretical and computational aspects)An integrated geomechanics study via multi-disciplinary approaches will be established to resolve these challenges. Funding to sponsor one PhD student is sought to carry out the study. Specifically, the study will begin with a field component to characterize the in situ stress state (and its variations) near the faults intersecting the Bedretto Underground Laboratory (BUL). This will proceed in accordance with the field geologic characterization by the SCCER-SoE at BUL. The measured in situ stress variations and the characterized fault structures will be correlated to identify a plausible causal relationship. Then, rock mechanical (elastic, visco-plastic) properties of the extracted fault zone rock samples will be characterized in the laboratory to establish a rigorous constitutive relationship and to quantify the effects of lithology and damage on rock rheology. This is followed by attempts to extrapolate the likely stress variations around the faults, based on the laboratory-derived relationship. The predicted stress variations will be compared with the in situ measurements, and the effects of stress variations on the effectiveness of stimulation and associated seismicity will be examined under different scenarios of stimulation strategies employed in the BUL field experiments.The project outcomes will bridge field observations and laboratory characterizations of reservoir-scale faults, representing a new level of understanding of the in situ stress field and its variations. Strong collaboration within the SCCER-SoE will advance the research on reservoir stimulation and seismicity mitigation. Furthermore, the laboratory/field workflow and the produced datasets by themselves are valuable because of the relative scarcity of relevant studies.